Lighting for dart frogs
Please advise me about lighting a vivarium for dart frogs. Should I provide lamps just for live plant growth or incorporate areas of UV as well? Are LED sources of light sufficient to grow plants in the ways that we see on the web and at shows?
There have been many advances in LED technology in recent years, with a huge array of LED plant grow products now on off er. Unfortunately, these are largely ineffective because of a misunderstanding of the way that plants use light. It is required in two main wavelengths for good photosynthesis, with plants needing light in the blue spectrum between 410-480nm, and also light in the red spectrum, from 610-680nm.
Light provided at these wavelengths will cause good vegetative growth, but only if the photosynthetically active radiation (PAR) is high enough to sustain the reactions in the plants. Although essential to PAR, blues and deep reds do not have all the energy required by plants to grow well.
The inclusion of a third colour, in the correct intensity, is essential to increase the PAR for this purpose. Full spectrum light in nature includes all of the colours in the correct balance. At Arcadia, we have been working on maximising live plant growth with LEDs for a long time now, and we have almost cracked it, but this technology is far from cheap.
The Europeans are tending to use high intensity discharge (HID) or metal halide systems in their dartfrog enclosures alongside T5 gro lamps. This provides columns of high potency UVB in the vivariums that the occupants can seek out when required. But it is worth stressing that these enclosures tend to be very, very big.
The ones that I have seen were over 1.5m (5ft) high. HID can be safely used for amphibians at these heights, simply because the heat and UVB decreases in power as the light travels down to the living space.
Currently, T5 is still by far the best way to provide full spectrum light for plant growth. I would certainly stay well away from LED tiles that only have red and blue LEDs. Lamps like the freshwater pro provide a very high colour rendition index (CRI) that will make your enclosure look fresh and provide the high levels of light (LUX) and PAR required for good plant growth. Plants themselves also use UVA and UVB in small amounts.
Amphibians and UVB
Dartfrogs will actively seek out UVB, using specialised vision to find the power that they require. We know that a 15% reduction in bone mass in amphibians can be seen easily on an X-ray and better morph rates and healthier adults have been recorded in groups that are kept with the provision of a natural UV index.
As in every avenue of herp keeping, so the only way to ascertain the correct exposure to light for a particular species is to start with the wild animal. Look for the average UV index of the amphibian’s country of origin and the habitat where it occurs. Increase or decrease the UV depending on local surroundings and the height above sea level. Provide more light to those species that are found in the hills or in less dense jungle areas.
What is known as leaf scatter illumination provides potent light in millions of shafts all over the jungle. A dartfrog simply needs to position itself in one of these shafts, to benefit from the available energy available. Even crepuscular and nocturnal species can benefit from the energy of light when they are in the open, even if they are sleeping.
Technology is catching up with our requirements and we will solution for amphibians in vivariums, tailored very closely to their needs. The perfect answer would be a high PAR lamp that provides the correct UVB emission. The closest that we have so far is the D3 HO T5, at 6% UVB and a Kelvin of 6k. In the future, I hope to see a hybrid of proven LED technology and T5 UVB lamps that will really offer the power that plants require, as well as providing the animals with the energy from light that they must have to meet their needs.
© John Courteney-Smith
Taken from “Practical Reptile Keeping” magazine